Britain’s Taranis unmanned combat air vehicle (UCAV) demonstrator has had a secretive upbringing.

With three flight-test phases now behind it—and possibly more to follow—the platform has and will continue to provide critical data that will help shape the next generation of UCAVs, including what is likely to be an Anglo-French UCAV demonstrator planned to fly in the 2020s.

But just testing such a platform has its own unique challenges, even for experienced aircraft manufacturers such as BAE Systems, faced with not only building the platform and integrating the systems but also with finding a way of testing it safely—as well as remotely, to preserve security around the project.

“We had to achieve the right flying properties, integrated communications . . . mission sensors and powerplant, integrate the exhaust . . . and ask how you control the vehicle,” said Paddy Bourne, Taranis chief engineer, speaking at the Royal Aeronautical Society in London on May 11. “All those things combine to make the design and the integration of the vehicle more complex.”

Taranis is the result of about a decade of research by BAE on a number of UAV demonstrators that tested autonomous flight, air data systems and tail-less configurations, all of which have fed into the Taranis program.

“The money for Taranis was focused on technology . . . and proving that technology,” explains Jon Wiggall, Taranis flight-test manager. To keep costs down it was decided not to do a full certification campaign. But to make sure there was no risk to people on the ground, the aircraft has been equipped with duplex hydraulics and electrical power generation systems, as well as a triplex flight control system.

“It [Taranis] has been designed to tolerate certain system failures so it does not immediately fall out of the sky if a single system goes wrong,” says Wiggall. But to be sure, BAE wanted a “sterile” testing area where no one was at risk if the aircraft crashed.

The Australian rocket test range at Woomera was selected. Apart from being largely home to “kangaroos and sheep,” according to Wiggall, the range’s area is about twice that available at the China Lake, California, naval weapons ranges, providing plenty of airspace for flight testing.

Along with being far from prying eyes, the area is also blessed with a benign electromagnetic environment, which reduces the need for electromagnetic compatibility testing. The team set boundaries within the range which would ensure that if control was lost the aircraft could be aborted before it exited the area.

A flight termination system, or so-called “big red button” would cut fuel to the engine, command full nose down elevons, and open the airbrakes. Full wheel brakes would also be activated if the aircraft was still on the ground.

Taranis flights were crewed by a commander, pilot, mission systems operator and a flight-test engineer who had direct access to five subject-matter experts and a range safety officer. Two Royal Air Force pilots also flew the platform during the test phases.

Flight testing was planned in the same way as for any manned aircraft, starting in the middle of the flight envelope and then progressively expanding to higher and lower altitudes and speeds; however, each flight-test point has to be programmed into Taranis as a waypoint.

“In a manned aircraft, we can ask the pilot to repeat test points . . . . There is more flexibility when you have a man in the cockpit,” says Wiggall. “On Taranis, the flights are preplanned, the progression is step-by-step, and you have to think carefully about what the aircraft is going to do.”

Another complication was the line-of-sight communication systems, which could result in data dropouts when the aircraft performed certain maneuvers, and test points would need repeating. Flights are programmed to perform key test points. Putting them close together allowed the engine to be throttled up or down quickly to check engine surge characteristics, for example. The waypoint metadata also contains maneuver codes that define the maneuver the aircraft will perform at the waypoint, as well as airspeed and altitude.

Taranis has three modes of flight. Automatic—the one in which the aircraft spends most of its time—flies it from waypoint to waypoint, while an autonomous mode allows the aircraft to plot its own route and self-navigate within a set of constraints. This is usually used when Taranis is searching for targets or performing its attack run and bomb-damage assessments, before it reenters automatic flight.

A manual, reversionary mode is also available, but was only ever used once, and then deliberately for just 90 sec., to make sure the aircraft behaved as simulated.

Phase 1 of flight trials tested the airframe, aerodynamics, air data and autonomy, and allowed the team to collect information so that the low-observable air data system could be used in the second phase, which allowed testing of the platform’s stealthy characteristics.

A third phase of trials was performed in 2015, but no information about them has been released by BAE or the U.K. Defense Ministry. Secrecy still surrounds the performance, specifications and even the number of flights performed by the platform.